<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>角向渐变</title>
    <style>
        body{
            background-color: black;
        }
        .box {
            margin: 200px auto;
            width: 400px;
            height: 300px;
            overflow: hidden;
            background-color: rgba(168, 239, 255, .1);
            position: relative;
            border-radius: 10px;
        }

        .box::after {
            position: absolute;
            content: "";
            width: 380px;
            height: 280px;
            top: 10px;
            left: 10px;
            background-color: #000;
            border-radius: 10px;
        }

        .conic {
            width: 100%;
            height: 100%;
            position: relative;
        }

        .conic::before {
            content: '';
            position: absolute;
            left: -50%;
            top: -50%;
            width: 200%;
            height: 200%;
            background: conic-gradient(transparent, rgba(168, 239, 255, 1), transparent 30%);
            animation: rotate 4s linear infinite;
        }

        @keyframes rotate {
            100% {
                transform: rotate(1turn);
            }

        }
    </style>
</head>

<body>
    <div class="box">
        <div class="conic">

        </div>
    </div>
</body>

</html>